The invention concerns a stent, in particular a coronary stent, as an intraluminal expansion element comprising a thin-walled, hollow-cylindrical base body of an X-ray transparent material having a surface area which has an open-worked, net shaped design owing to recesses and comprising at least one X-ray opaque element or region.
European patent document EP-B1 0 364 787 discloses an expandable, intraluminal element with at least one thin-walled, tube-shaped segment (in the following called a stent). The surface area of the stent has an open-worked, net-shaped design and comprises recesses, which are limited by web-like elements with low material strength that extend in a straight-line in the axial and circumferential directions. The web-like elements consist of the remaining tube wall where the material was removed in the region of the recesses. Four of these web-like elements, together with the connecting pieces provided at their ends, form a so-called "expansible region" of the stent surface area.
Such stents are expanded during an operation, e.g. to remove a stenosis, under the effect of forces that act from the inside toward the outside and by using a tubular dilator admitted with compressed gas. Despite the deformation, the stent retains its tubular shape and dilates the vessel that is restricted as a result of deposits.
The above-described stents are produced from biocompatible materials such as stainless steel, titanium or other metals. Titanium stents have proven to be particularly useful with respect to physical tolerance, options for medical use and mechanical workability.
However, for the wall thicknesses used for stents, the metals used most often are essentially X-ray transparent, and stents fashioned from these cannot be seen by the physician when using X-rays. Nevertheless, the identification of the stent position with the aid of a suitable monitor has proven to be very critical for the correct handling.
A stent visible in an X-ray is disclosed in European patent document EP-A-O 709 068, for which the visibility in the X-ray is achieved through a coating with a metal having a high atomic weight or through expanded, e.g. ring-shaped, extensions on the individual ends of the meshes.
German patent document DE-U-296 07 916 discloses a stent with a segment visible in the X-ray, which is produced in particular by welding together two prefabricated hollow cylinders made of X-ray transparent or X-ray reflecting material.
The accuracy of the stent position determination can still be improved for both of the aforementioned arrangements.